CN101650164B - Phase unwrapping method based on malposition fringes in three-dimensional scanning system - Google Patents

Phase unwrapping method based on malposition fringes in three-dimensional scanning system Download PDF

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CN101650164B
CN101650164B CN2009100351789A CN200910035178A CN101650164B CN 101650164 B CN101650164 B CN 101650164B CN 2009100351789 A CN2009100351789 A CN 2009100351789A CN 200910035178 A CN200910035178 A CN 200910035178A CN 101650164 B CN101650164 B CN 101650164B
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striped
phase
malposition
fringes
width
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CN101650164A (en
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达飞鹏
王新
盖绍彦
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Jiangsu Hengyuan Silk Group Co., Ltd.
Southeast University
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Southeast University
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Abstract

The invention provides a phase unwrapping method based on malposition fringes in a three-dimensional scanning system, mainly relating to the reverse engineering; the three-dimensional scanning system is used for carrying out phase unwrapping according to the malposition fringes; according to the needs, four grating phase shifting pictures with 90-degree phase shifting are designed, and a malposition fringe grating is designed according to the coding requirements for designing the malposition fringes, and the four grating phase shifting pictures are respectively projected to an object to be measured, and then a CCD is used for back-shooting to a computer. According to the four phase shifting pictures, a folding phase shifting picture with phase value which is in a range from -Pi to Pi is obtained by a phase shifting method; the difference of the malposition fringe pictures and the four phase shifting pictures are made respectively, so as to obtain four fringe differential pictures, the fringe characteristics of all positions in the malposition fringe grating are determined by zero fringe information in the differential pictures, and then the coding information of the malposition fringes is combined again, so as to determine the order of each single-cycle fringe in the malposition fringes, which is obtained by the CCD and guide the folding phase to be unwrapped. The whole computing process does not depend on routes, thereby having good real-time performance.

Description

In the 3 D scanning system based on the phase developing method of malposition fringes
Technical field
The present invention is mainly concerned with in the reverse-engineering, finds the solution the method for phase place according to four step phase shift stripeds and malposition fringes with 3 D scanning system.The technical field that belongs to three-dimensional information reconstruct.
Background technology
Reverse-engineering (Reverse Engineering, RE) technology is the later stage eighties 20th century to appear at the new technology in the advanced manufacturing field, it generally comprises four basic links: three-dimensional body detects and conversion (acquisition of physical data), data pre-service (put cloud processing, identification, look splicing more), the foundation of cad model (surface reconstruction), the moulding of CAM product.Great majority mainly concentrate in the reverse reconstruct in kind about the research of reverse-engineering, and promptly the cad model reconstruct of product material object and the manufacture view of final products are called " reverse-engineering in kind ".
Three-D profile detects and reconfiguration technique is a branch of computer image processing technology, be that computer vision and computer graphic image are handled a research direction that combines, it all has a wide range of applications in fields such as the production automation, robot vision, CAD, virtual reality and the diagnosis of medical science reflection.
The optical grating projection method is a kind of in the three-dimensional detection technique, has the complete noncontact of measuring process, data space resolution height, disposable moment projection and realizes that directly the three dimensions body form detects and obtain the characteristics of three-dimensional information.Have multiple advantages such as low, with low cost to environmental requirement, that use is easy to operate in actual applications.
Three-dimensional measurement based on optical grating projection projects to raster pattern the measured object surface exactly, obtains the grating picture of distortion by video camera, and determines the elevation information of profile phase to reference planes by the deformation quantity and the relation of height.When optical grating projection was to body surface, periodically the phase place of grating just was subjected to the modulation of body surface height profile, formed deformed grating, had the three-dimensional information of object in the deformed grating.Accurately obtain being subjected to the phase information after the object height modulation, the line phase of going forward side by side launches, and obtains the object deformation quantity, plays a part crucial for the three-dimensional information that finally obtains object.
In grating fringe figure, add known or unknown Chang Xiangwei by giving the field of behaviour to be asked, obtain new bar graph, promptly increase solving condition.Thisly increase some constant phase and obtain several bar graphs, be called phase-shift method in order to find the solution the method for the field of behaviour by the bar graph field of behaviour being carried out phase shift.Phase-shift method can provide than the more high-precision result of additive method, the more important thing is, it does not have the phase symbol ambiguity problem.This is because several phase shifts figure provides more information than single width figure.The phase value that obtains by said method is in-π～π scope, be (wrapped) that folds, in order to obtain the unique phase value of the whole audience, before from PHASE DISTRIBUTION, deriving measured parameter, must go out 2 unknown π multiple transition to all pixel identification, thus the phase decoding that obtains restoring.This process is called phase unwrapping (phase unwrapping) or phase retrieval.
Adopt traditionally when separating phase method, because the not independence between pixel, be interrupted the district and the noise spot place is prone to " backguy " phenomenon at physics, local error will have influence on the overall situation; The patent documentation phase developing method of Gray code " in the 3 D scanning system based on " is according to the binary-coded requirement in space design 7 width of cloth two minutes projection grating figure progressively, utilizes the method for Gray code to determine the cycle at phase place place, carries out phase unwrapping thus.It is simple relatively that the method is carried out phase developing method, can well distinguish physics discontinuities and noise, do not rely on the path, do not have error propagation, can access the cycle accurately.But this method need design 7 width of cloth two minutes projection grating figure has progressively increased the time cost of systematic survey greatly, and it is relatively poor to measure real-time.
Summary of the invention
Technical matters:, the object of the present invention is to provide in a kind of 3 D scanning system accuracy height, real-time phase developing method preferably at existing in prior technology shortcoming and restriction.This method at first obtains accurate wrapped phase by four step phase-shift methods, utilize a width of cloth malposition fringes to phase unwrapping on this basis again, computation process does not rely on the path, there is not error propagation, can well distinguish physics discontinuities and noise, can access the cycle accurately, and have good real time performance.
Technical scheme: design is designated as the fundamental element that constitutes stripe pattern with the monocycle striped of 4 equal lengths of 90 ° of phase shifts; Be corresponding 4 width of cloth phase shift stripe patterns that generate of unit with each fundamental element respectively; Be that unit encodes with 4 monocycle stripeds simultaneously, generate the malposition fringes image; To generate stripe pattern and be projected on the testee, and use the ccd video camera photographic images, fetch computing machine analysis.According to 4 width of cloth phase shift figure, utilize phase-shift method to obtain phase value folding (wrapped) phase diagram in-π～π scope; Two width of cloth stripeds are identical at the locational fundamental element of certain Cycle Length, obtain the image of two width of cloth stripeds under identical conditions, and gray scale is subtracted each other and obtained striped difference figure on same position; In theory, on the identical position of fundamental element, the fringe gray level value among the difference figure is 0, is referred to as 0 value striped; The malposition fringes image is poor with 4 width of cloth phase shifted images respectively, obtain 4 width of cloth striped difference figure; By difference figure is carried out the accurate localization process in Threshold Segmentation, filtering and border, obtain accurate 0 value stripe information; The corresponding respectively position distribution of 4 kinds of unit stripeds in the malposition fringes image that has 90 ° phase shift of 0 value fringe position among 4 width of cloth difference figure; Like this, can utilize 0 value stripe information among the striped difference figure to determine each locational streak feature in the malposition fringes image, then in conjunction with the coded message of malposition fringes, determine the order of each striped in the malposition fringes that video camera obtains, instruct wrapped phase figure to launch with this, obtain the unique phase value of the whole audience.
The present invention is based on the phase developing method of malposition fringes, step is as follows:
Step 1: design bar graph and 1 width of cloth malposition fringes figure that 4 width of cloth have 90 ° of phase shifts;
Step 1.1: design 4 width of cloth phase shift figure, the phase shift that makes 4 width of cloth figure respectively is 0,0.5 π, π, 1.5 π; Each figure is expressed as:
I 1(x，y)＝cos(2πfx)
I 2(x，y)＝cos(2πfx+0.5π)
I 3(x，y)＝cos(2πfx+π)
I 4(x，y)＝cos(2πfx+1.5π)
Wherein f is the striped frequency, and f=1/T, T are the cycle striped, and unit is a pixel.The phase shift stripe pattern is the striped of sinusoidal variations on line direction, and among 4 width of cloth phase shift figure, the cycle of striped is all T, and the initial phase difference of each cycle striped is respectively 0,0.5 π, π, 1.5 π.
Step 1.2: design malposition fringes figure: initial phase is respectively 0,0.5 π, π, 1.5 π, the cycle is that four monocycle stripeds of T carry out coded combination, generates malposition fringes.Malposition fringes requires: (1) every two adjacent monocycle striped initial phase differences; (2) be one group with three adjacent monocycle stripeds, any two groups can not duplicate; (3) make the striped length maximum of compound condition (1), (2).
For convenient expression, initial phase is respectively 0,0.5 π, π, 1.5 π, cycle are that four monocycle stripeds of T are expressed as a, b, c, d respectively; Malposition fringes is I 0
The malposition fringes coding step is as follows:
Step 1.2.1:, list all adjacent 3 cycle striped s according to the requirement of permutation and combination principle and malposition fringes i, 1≤i≤36, all s iSet is s,
s＝{aba，abc，abd，aca，acb，acd，ada，adb，adc，bab，bac，bad，bca，bcb，bcd，bda，bdb，bdc，cab，cac，cad，cba，cbc，cbd，cda，cdb，cdc，dab，dac，dad，dba，dbc，dbd，dca，dcb，dcd}
Wherein, s 1=abc represents that striped length is three cycles, and the striped at first period position place is a, and the striped of second period position is b, and the striped at the 3rd period position place is a; Set up empty sequence I 0
Step 1.2.2: from s, select s iAs homing sequence, list I in 0, and with s iFrom s, delete;
Step 1.2.3: get s iBack 2 unit quantities as s j(1≤j≤36, preceding 2 elements of j ≠ i) are sought the s that satisfies condition from s j, with s jLast element is mended into I 0, make s i=s j, and from s, delete s j
Step 1.2.4: repeating step 1.2.3 to s is empty, can set up I fully 0
Make s among the step 1.2.2 i=abc can get malposition fringes by above-mentioned coding method and is:
I 0＝abcadbdacbabdcdcacdbcbcdadcbdbacabadab
Malposition fringes is made up of a plurality of monocycle stripeds, in order to represent the logical place of each cycle striped, compose a value for each striped, be referred to as the order of striped, among the present invention, the order of setting Far Left monocycle striped is 1, and the order of striped increases progressively to the right, promptly turn right from leftmost cycle striped, the order of each monocycle striped increases progressively with 1;
Step 2: malposition fringes contains 38 cycle stripeds, satisfies the needs of measuring.The periodicity of 4 width of cloth phase shift stripeds of design is got identical value with malposition fringes, and set the size of fringe period and image according to measurement requirement, and generate 5 width of cloth projection grating images, through projector it is projected body surface, for each width of cloth projection grating figure, video camera is all got figure once to object.In order to guarantee to get the quality of figure, reduce during shooting as far as possible and walk about, not in the light acute variation, under the extremely strong situation of surround lighting object is taken;
Step 3:, calculate wrapped phase to collecting to such an extent that 4 width of cloth phase-shifted grating images are handled;
4 width of cloth phase-shifted grating images that collect are:
Figure G2009100351789D00041
Figure G2009100351789D00042
Figure G2009100351789D00043
Figure G2009100351789D00044
Wherein, f ' is for collecting the frequency of striped in the raster image, and f '=1/T ', T ' are the cycle of striped, and unit is a pixel, I ' i(x, y) (i=1,2,3,4) are the gray-scale value of i width of cloth phase-shifted grating figure, I 0(x y) is the background value of bar graph, γ (x y) is the modulate intensity function,
Figure G2009100351789D00045
Be the field of behaviour to be asked, suppose 4 width of cloth figure in same light field, background gray levels is identical.According to triangle formula:
cos α 1 - cos α 2 = - 2 sin α 1 + α 2 2 sin α 1 - α 2 2
With I i(x, y) the substitution following formula gets:
Figure G2009100351789D00047
Figure G2009100351789D00048
To its negate tan, just can obtain the main value field of behaviour:
Figure G2009100351789D00049
Can obtain wrapped phase information according to top formula;
Step 4: the malposition fringes raster pattern that collects is subtracted each other with 4 width of cloth phase-shifted grating figure respectively, obtain 4 width of cloth striped difference figure,, determine the order of each cycle striped in the malposition fringes grating by 0 value grating among every width of cloth striped difference figure is positioned;
The malposition fringes raster pattern that collects is
Figure G2009100351789D000410
(x y) is coordinate points in the image, β (x, y) ∈ { 0,0.5 π, π, 1.5 π }, and when f ' x is integer β (x, value y) changes, be β (x, value y) is constant in each cycle striped, changes during week, Changing Pattern is by the decision of the coding of malposition fringes.As I 0Corresponding respectively this initial phase of=abcadbdacbabdcdcacdbcbcdadcbdbdcabadab, a, b, c, d is 0,0.5 π, π, and four monocycle stripeds of 1.5 π, then
β ( x , y ) = 0 , x ∈ ( 1 , T ′ ] β ( x , y ) = 0.5 π , x ∈ ( T ′ , 2 T ′ ] β ( x , y ) = π , x ∈ ( 2 T ′ , 3 T ′ ] · · ·
Corresponding malposition fringes grating
I o ′ ( x , y ) = I 1 ′ ( x , y ) , x ∈ ( 1 , T ′ ] I o ′ ( x , y ) = I 2 ′ ( x , y ) , x ∈ ( T ′ , 2 T ′ ] I o ′ ( x , y ) = I 3 ′ ( x , y ) , x ∈ ( 2 T ′ , 3 T ′ ] · · ·
Step 4.1: 4 width of cloth phase-shifted grating images are subtracted each other with the malposition fringes raster pattern respectively obtain 4 width of cloth striped difference figure,, therefore can occur 0 value striped among every in theory width of cloth difference figure because on same position, there is identical cycle striped in the phase shift striped with malposition fringes.Because the influence of factors such as peripheral light intensity, noise, the obscurity boundary of 0 value striped and gray-scale value are not strict to be 0, at this striped difference figure is carried out Threshold Segmentation, filtering, and utilizes the boundary information among the wrapped phase figure that the border of each cycle striped is positioned;
Step 4.1.1: adopt less threshold value that every width of cloth striped difference figure is carried out Threshold Segmentation, gray-scale value belongs to greater than the point of this threshold value and is non-0 value striped, and it is 1 that gray-scale value is composed, otherwise to compose be 0 to gray-scale value;
Gray-scale value is 0 point among the step 4.1.2:4 width of cloth striped difference figure, is defined as dash area, and this part does not participate in following any calculating;
Step 4.1.3: adopt the contrast filtering algorithm to eliminate noise to the striped difference figure after the Threshold Segmentation; Under same coordinate, the position zero lap of all the 0 value stripeds among 4 width of cloth striped difference figure and be covered with non-shaded portion, therefore concerning 4 width of cloth striped difference figure, noise among a certain width of cloth striped difference figure inevitable with other figure in the coordinate of 0 value striped overlapping, because the width of 0 discrete value striped and width and the scope that scope is far longer than noise, so but by the filtering noise to the scope contrast;
Step 4.1.4: determine each striped border: every some phase place in the wrapped phase is asked for phase gradient according to wrapped phase
Figure G2009100351789D00052
Wherein, (x y) is the coordinate of wrapped phase figure mid point, grad (x, y) be (x, phase gradient y),
Figure G2009100351789D00053
Be wrapped phase.Phase gradient is the striped frontier point greater than the point of gradient mean value;
Step 4.1.5: to the gray-scale value among the filtered poor figure is 0 striped, if its most zones are positioned at certain two border, then with the boundary line of these two borders as 0 value striped, thereby accurately locatees each 0 value striped;
Step 4.2: determine malposition fringes grating I ' 0Composition sequence.Malposition fringes I ' 0In, be that 0 phase-shifted grating and malposition fringes grating subtract each other the identical position of 0 value striped among the poor figure that obtains with initial phase, corresponding striped is a ', the striped that a ' obtains for a distortion; Be that the phase-shifted grating of 0.5 π and malposition fringes grating subtract each other the identical position of 0 value striped among the poor figure that obtains with initial phase, corresponding striped is b ', the striped that b ' obtains for the b distortion; Be that the phase-shifted grating of π and malposition fringes grating subtract each other the identical position of 0 value striped among the poor figure that obtains with initial phase, corresponding striped is c ', the striped that c ' obtains for the c distortion; Be that the phase-shifted grating of 1.5 π and malposition fringes grating subtract each other the identical position of 0 value striped among the poor figure that obtains with initial phase, corresponding striped is d ', the striped that d ' obtains for the d distortion;
Step 4.3: the accurate order of determining each cycle striped in the malposition fringes grating.Order is the build-in attribute of striped, and when striped was subjected to the modulation of body surface height and condition effect such as bias light, body surface reflectivity and changes, the order of each striped was constant.I ' 0In each striped by I 0In striped obtain by certain variation, so only need determine I ' 0In each striped at I 0In corresponding striped, can determine I ' 0In the order of each striped.
By the cataloged procedure of malposition fringes as can be known, I 0In the sequence formed of per 3 cycle stripeds be unique; So to I ' 0In each striped, two stripeds that are adjacent are formed one 3 cycle striped sequence, at I 0The unique sequence corresponding of middle searching with it, corresponding fringe order is inferior identical in the sequence, promptly draws the accurate order of each monocycle striped in the malposition fringes grating thus;
Step 5: wrapped phase is launched, obtain absolute phase values.Wrapped phase is tried to achieve by 4 width of cloth phase-shifted gratings, and each phase shift cycle fringe position and corresponding each phase cycling position, therefore, the order of the striped at same position place is identical in the order of each phase cycling and the phase shift striped, and phase shift striped and malposition fringes are the stripeds with the same period length variations, so that the striped order of the two distributes is identical, thereby, according to the order of each cycle striped in the malposition fringes grating, can accurately obtain the order of each phase cycling, according to formula:
Figure G2009100351789D00061
K=0,1,2 ... wherein,
Figure G2009100351789D00062
Be the phase value of certain point among the wrapped phase figure, k represents this order at wrapped phase figure, and (i j) is the absolute phase values after this some expansion to Φ, can draw and launch the unique phase diagram of back whole audience phase place;
Beneficial effect: compared with prior art, the present invention has following advantage:
Be the basic composition amount at first with 4 monocycle phase shift stripeds, coding generates malposition fringes, in the malposition fringes, the striped sequence that three composition amounts that two adjacent composition amounts are different and adjacent form is unique in malposition fringes, the present invention utilizes the permutation and combination principle in cataloged procedure, the exhaustive combination that goes out all three composition amounts that satisfy condition makes the malposition fringes length maximum of generation, thereby helps the global measuring of object; Secondly, in to folding phase unwrapping process, only utilize a width of cloth malposition fringes to help launch phase place, saved the complexity of projection time and projected fringe coding greatly, and the present invention does not rely on the path in computation process, does not have error propagation, can well distinguish physics discontinuities and noise, can access the cycle accurately, and have good real time performance.Therefore, the present invention can obtain accurate, complete phase unwrapping figure easily and efficiently, lays a good foundation for finally obtaining accurate three-dimensional information.
Description of drawings
Fig. 1 is based on the phase unwrapping process flow diagram of malposition fringes.
Embodiment
Show below in conjunction with accompanying drawing the specific embodiment of the present invention is further described.According to said method, in Windows operating system, realized the operation of phase unwrapping with the C++ programming by the VC++6.0 platform.This example utilizes 3 D scanning system the motorcycle backplate to be carried out phase place is obtained and phase unwrapping, obtains accurate, complete whole audience phase information.
4 amplitude grating phase shift figure and a width of cloth malposition fringes raster pattern according to 90 ° of phase shifts of actual measurement Demand Design band are projected to it on testee, are taken the photograph by CCD then and are back to computing machine, according to 4 width of cloth phase shift figure, utilize phase-shift method, according to
Figure G2009100351789D00071
Can obtain the wrapped phase figure of phase value in-π～π scope; The malposition fringes image is poor with 4 width of cloth phase shifted images respectively, obtain 4 width of cloth striped difference figure; Identical ingredient in malposition fringes and the every width of cloth phase shift striped, the value of showing as is 0 striped in difference figure, by striped difference figure is carried out the accurate localization process in Threshold Segmentation, filtering and border, obtains accurate 0 value stripe information; 0 fringe position among 4 width of cloth difference figure has been represented the position distribution of 4 kinds of monocycle stripeds in the malposition fringes image of the phase shift that has 90 ° respectively, like this, can determine the streak feature of each position in the malposition fringes image according to 0 value stripe information among the difference figure, then in conjunction with the coded message of malposition fringes, determine the order of each the monocycle striped in the malposition fringes that video camera obtains, thereby instruct wrapped phase to launch, obtain the unique phase value of the whole audience.
Process flow diagram of the present invention as shown in Figure 1, the specific implementation step is as follows:
Step 1: design bar graph and 1 width of cloth malposition fringes figure that 4 width of cloth have 90 ° of phase shifts;
Step 1.1: design 4 width of cloth phase shift figure, the phase shift that makes 4 width of cloth figure respectively is 0,0.5 π, π, 1.5 π; Each figure is expressed as:
I 1(x，y)＝cos(2πfx)
I 2(x，y)＝cos(2πfx+0.5π)
I 3(x，y)＝cos(2πfx+π)
I 4(x，y)＝cos(2πfx+1.5π)
Wherein f is the striped frequency, and f=1/T, T are the cycle striped, and unit is a pixel.The phase shift stripe pattern is the striped of sinusoidal variations on line direction, and among 4 width of cloth phase shift figure, the cycle of striped is all T, and the initial phase difference of each cycle striped is respectively 0,0.5 π, π, 1.5 π.
Step 1.2: design malposition fringes figure: initial phase is respectively 0,0.5 π, π, 1.5 π, the cycle is that four monocycle stripeds of T carry out coded combination, generates malposition fringes.Initial phase is respectively 0,0.5 π, π, 1.5 π, cycle are that four monocycle stripeds of T are expressed as a, b, c, d respectively; Malposition fringes is I 0
The malposition fringes coding step is as follows:
Step 1.2.1:, list all adjacent 3 cycle striped s according to the requirement of permutation and combination principle and malposition fringes i, 1≤i≤36, all s iSet is s,
s＝{aba，abc，abd，aca，acb，acd，ada，adb，adc，bab，bac，bad，bca，bcb，bcd，bda，bdb，bdc，cab，cac，cad，cba，cbc，cbd，cda，cdb，cdc，dab，dac，dad，dba，dbc，dbd，dca，dcb，dcd}
Wherein, s 1=abc represents that striped length is three cycles, and the striped at first period position place is a, and the striped of second period position is b, and the striped at the 3rd period position place is a; Set up empty sequence I 0
Step 1.2.2: from s, select s iAs homing sequence, list I in 0, and with s iFrom s, delete;
Step 1.2.3: get s iBack 2 unit quantities as s j(1≤j≤36, preceding 2 elements of j ≠ i) are sought the s that satisfies condition from s j, with s jLast element is mended into I 0, make s i=s j, and from s, delete s j
Step 1.2.4: repeating step 1.2.3 to s is empty, can set up I fully 0
Make s among the step 1.2.2 i=abc can get malposition fringes by above-mentioned coding method and is:
I 0＝abcadbdacbabdcdcacdbcbcdadcbdbacabadab
Malposition fringes I 0Order be that unit turns right from the left side and increases progressively with 1 with the period T.
Step 2: malposition fringes contains 38 cycle stripeds, satisfies the needs of measuring.The periodicity of 4 width of cloth phase shift stripeds of design is got identical value with malposition fringes, and set the size of fringe period and image according to measurement requirement, and generate 5 width of cloth projection grating images, through projector it is projected body surface, for each width of cloth projection grating figure, video camera is all got figure once to object.
Step 3:, calculate wrapped phase to collecting to such an extent that 4 width of cloth phase-shifted grating images are handled;
4 width of cloth phase-shifted grating images that collect are:
Figure G2009100351789D00081
Figure G2009100351789D00082
Figure G2009100351789D00083
Figure G2009100351789D00084
Wherein, f ' is for collecting the frequency of striped in the raster image, and f '=1/T ', T ' are the cycle of striped, and unit is a pixel, I ' i(x, y) (i=1,2,3,4) are the gray-scale value of i width of cloth image, I 0(x y) is the background value of bar graph, γ (x y) is the modulate intensity function,
Figure G2009100351789D00085
Be the field of behaviour to be asked.Suppose 4 width of cloth figure in same light field, background gray levels is identical, according to formula:
Figure G2009100351789D00086
Ask for wrapped phase.
Step 4: the malposition fringes raster pattern and 4 width of cloth phase-shifted grating figure that collect are subtracted each other respectively, obtain 4 width of cloth striped difference figure, 0 value striped among every width of cloth striped difference figure is positioned, determine the order of each cycle striped in the malposition fringes grating by calculating;
The malposition fringes raster pattern that collects is
Figure G2009100351789D00087
(x y) is coordinate points in the image, β (x, y) ∈ { 0,0.5 π, π, 1.5 π }, and when f ' x is integer β (x, value y) changes, be β (x, value y) is constant in each cycle striped, changes during week, Changing Pattern is by the decision of the coding of malposition fringes.
Step 4.1: 4 width of cloth phase-shifted grating images are subtracted each other with the malposition fringes raster pattern respectively obtain 4 width of cloth striped difference figure, figure carries out Threshold Segmentation, filtering to the striped difference, and utilizes the boundary information among the wrapped phase figure that the border of each cycle striped is positioned;
Step 4.1.1: adopt less threshold value that every width of cloth striped difference figure is carried out Threshold Segmentation, gray-scale value belongs to greater than the point of this threshold value and is non-0 value striped, and it is 1 that gray-scale value is composed, otherwise to compose be 0 to gray-scale value;
Gray-scale value is 0 point among the step 4.1.2:4 width of cloth striped difference figure, is defined as dash area, and this part does not participate in following any calculating;
Step 4.1.3: adopt the contrast filtering algorithm to eliminate noise to the striped difference figure after the Threshold Segmentation; Under same coordinate, the position zero lap of all the 0 value stripeds among 4 width of cloth striped difference figure and be covered with non-shaded portion, therefore concerning 4 width of cloth striped difference figure, noise among a certain width of cloth striped difference figure inevitable with other figure in the coordinate of 0 value striped overlapping, because the width of 0 discrete value striped and width and the scope that scope is far longer than noise, so but by the filtering noise to the scope contrast;
Step 4.1.4: determine each striped border: every some phase place in the wrapped phase is asked for phase gradient according to wrapped phase
Figure G2009100351789D00091
Wherein, (x y) is the coordinate of wrapped phase figure mid point, grad (x, y) be (x, phase gradient y),
Figure G2009100351789D00092
Figure G2009100351789D00093
Be wrapped phase.Phase gradient is the striped frontier point greater than the point of gradient mean value.
Step 4.1.5: to the gray-scale value among the filtered poor figure is 0 striped, if its most zones are positioned at certain two border, then with the boundary line of these two borders as 0 value striped, thereby accurately locatees each 0 value striped;
Step 4.2: determine malposition fringes grating I ' 0Composition sequence.Malposition fringes I ' 0In, be that 0 phase-shifted grating and malposition fringes grating subtract each other the identical position of 0 value striped among the poor figure that obtains with initial phase, corresponding striped is a ', the striped that a ' obtains for a distortion; Be that the phase-shifted grating of 0.5 π and malposition fringes grating subtract each other the identical position of 0 value striped among the poor figure that obtains with initial phase, corresponding striped is b ', the striped that b ' obtains for the b distortion; Be that the phase-shifted grating of π and malposition fringes grating subtract each other the identical position of 0 value striped among the poor figure that obtains with initial phase, corresponding striped is c ', the striped that c ' obtains for the c distortion; Be that the phase-shifted grating of 1.5 π and malposition fringes grating subtract each other the identical position of 0 value striped among the poor figure that obtains with initial phase, corresponding striped is d ', the striped that d ' obtains for the d distortion;
Step 4.3: the accurate order of determining each cycle striped in the malposition fringes grating.To I ' 0In each striped, two stripeds that are adjacent are formed one 3 cycle striped sequence, at I 0The unique sequence corresponding of middle searching with it, corresponding fringe order is inferior identical in the sequence, draws the accurate order of each monocycle striped in the malposition fringes grating thus;
Step 5: wrapped phase is launched, obtain absolute phase values.
According to the order of each monocycle striped in the malposition fringes grating, accurately obtain the order of each phase cycling, according to formula:
Figure G2009100351789D00095
K=0,1,2 ... wherein,
Figure G2009100351789D00096
Be the phase value of certain point among the wrapped phase figure, k represents this order at wrapped phase figure, and (i j) is the absolute phase values after this some expansion to Φ, can draw and launch the unique phase diagram of back whole audience phase place.

Claims (2)

  1. In the 3 D scanning system based on the phase developing method of malposition fringes, it is characterized in that according to 4 amplitude grating phase shift figures and the width of cloth malposition fringes raster pattern of the coding requirement of actual measurement demand and malposition fringes design with 90 ° of phase shifts, it is projected on the testee, take the photograph by video camera then and be back to computing machine, according to 4 width of cloth phase shift figure, utilize phase-shift method, according to
    Figure FSB00000315993300011
    Obtain the wrapped phase of phase value in-π～π scope; The malposition fringes image is poor with 4 width of cloth phase shifted images respectively, obtain 4 width of cloth striped difference figure; Identical ingredient in malposition fringes and the every width of cloth phase shift striped, the value of showing as is 0 striped in difference figure, by carrying out the accurate localization process in Threshold Segmentation, filtering and border to differing from figure, obtains accurate 0 value stripe information; 0 value fringe position among 4 width of cloth difference figure has been represented the position distribution of 4 kinds of monocycle stripeds in the malposition fringes image of the phase shift that has 90 ° respectively, like this, can utilize 0 value stripe information among the striped difference figure to determine each locational streak feature in the malposition fringes image, then in conjunction with the coded message of malposition fringes, determine the order of each the monocycle striped in the malposition fringes that video camera obtains, instruct wrapped phase figure to launch with this, obtain the unique phase value of the whole audience;
    The concrete operations step is as follows:
    Step 1: design bar graph and 1 width of cloth malposition fringes figure that 4 width of cloth have 90 ° of phase shifts;
    Step 2: the periodicity of 4 width of cloth phase shift stripeds that will design is got identical value with malposition fringes, and set the size of fringe period and image according to measurement requirement, generate 5 width of cloth projection grating images, through projector it is projected body surface, every pair of object throws a width of cloth projection grating, and video camera is all got figure once to object;
    Step 3:, calculate wrapped phase to collecting to such an extent that 4 width of cloth phase-shifted grating images are handled;
    4 width of cloth phase-shifted grating images that collect are:
    Figure FSB00000315993300012
    Figure FSB00000315993300013
    Figure FSB00000315993300014
    Figure FSB00000315993300015
    Wherein, f ' is for collecting the frequency of striped in the raster image, and f '=1/T ', T ' are the cycle of striped, and unit is a pixel; I ' i(x y) is the gray-scale value of i width of cloth image, i=1,2,3,4; I 0(x y) is the background value of bar graph; (x y) is the modulate intensity function to γ;
    Figure FSB00000315993300016
    Be the field of behaviour to be asked; Suppose 4 width of cloth figure in same light field, background gray levels is identical, according to formula:
    Figure FSB00000315993300017
    Ask for wrapped phase;
    Step 4: the malposition fringes raster pattern and 4 width of cloth phase-shifted grating figure that collect are subtracted each other respectively, obtain 4 width of cloth striped difference figure,, determine the order of each monocycle striped in the malposition fringes raster pattern by 0 value striped among every width of cloth striped difference figure is positioned;
    The malposition fringes raster pattern that collects is
    Figure FSB00000315993300021
    (x y) is coordinate points in the image, β (x, y) ∈ { 0,0.5 π, π, 1.5 π }, and when f ' x is integer β (x, value y) changes, be β (x, value y) is constant in each cycle striped, changes during week, Changing Pattern is by the decision of the coding of malposition fringes;
    Step 5: wrapped phase is launched, obtain absolute phase values;
    According to the order of each monocycle striped in the malposition fringes grating, accurately obtain the order of each phase cycling, according to formula:
    Figure FSB00000315993300022
    K=0,1,2 ..., wherein,
    Figure FSB00000315993300023
    Be the phase value of certain point among the wrapped phase figure, k represents this order at wrapped phase figure, and (i j) is the absolute phase values after this some expansion to Φ, can draw and launch the unique phase diagram of back whole audience phase place;
    In the step 1, design that 4 width of cloth have the bar graph of 90 ° of phase shifts and the method for 1 width of cloth malposition fringes figure is:
    Step 1.1: design 4 width of cloth phase shift figure, the phase shift that makes 4 width of cloth figure respectively is 0,0.5 π, π, and 1.5 π, each figure is expressed as:
    I 1(x，y)＝cos(2πfx)
    I 2(x，y)＝cos(2πfx+0.5π)
    I 3(x，y)＝cos(2πfx+π)
    I 4(x，y)＝cos(2πfx+1.5π)
    Wherein f is the striped frequency, and f=1/T, T are the cycle striped, and unit is a pixel; The phase shift stripe pattern is the striped of sinusoidal variations on line direction, and among 4 width of cloth phase shift figure, the cycle of striped is all T, and the initial phase difference of each cycle striped is respectively 0,0.5 π, π, and 1.5 π,
    Step 1.2: design malposition fringes figure: initial phase is respectively 0,0.5 π, π, 1.5 π, the cycle is that four monocycle stripeds of T carry out coded combination, generates malposition fringes; Initial phase is respectively 0,0.5 π, π, 1.5 π, cycle are that four monocycle stripeds of T are expressed as a, b, c, d respectively; Malposition fringes is expressed as I o,
    The malposition fringes coding step is as follows:
    Step 1.2.1:, list all adjacent 3 cycle striped s according to the requirement of permutation and combination principle and malposition fringes i, 1≤i≤36, all s iSet is s,
    s＝{aba，abc，abd，aca，acb，acd，ada，adb，adc，bab，bac，bad，
    bca，bcb，bcd，bda，bdb，bdc，cab，cac，cad，cba，cbc，cbd，
    Cda, cdb, cdc, dab, dac, dad, dba, dbc, dbd, dca, dcb, dcd} set up empty sequence I o
    Step 1.2.2: from s, select s iAs homing sequence, list I in o, and with s iFrom s, delete;
    Step 1.2.3: get s iBack 2 unit quantities as s j(1≤j≤36, preceding 2 elements of j ≠ i) are sought the s that satisfies condition from s j, with s jLast element is mended into I o, make s i=s j, and from s, delete s j
    Step 1.2.4: repeating step 1.2.3 to s is empty, can set up I fully o
    Make s among the step 1.2.2 i=abc can get malposition fringes by above-mentioned coding method and is:
    I o＝abcadbdacbabdcdcacdbcbcdadcbdbacabadab
    Malposition fringes I oOrder be that unit turns right from the left side and increases progressively with 1 with the period T.
  2. 2. in the 3 D scanning system as claimed in claim 1 based on the phase developing method of malposition fringes, it is characterized in that in the step 4, the malposition fringes raster pattern and 4 width of cloth phase-shifted grating figure that collect are subtracted each other respectively, obtain 4 width of cloth striped difference figure, by calculating 0 value striped among every width of cloth striped difference figure is positioned, determine that the method for the order of each cycle striped in the malposition fringes grating is;
    Step 4.1: 4 width of cloth phase-shifted grating images are subtracted each other with the malposition fringes raster pattern respectively obtain 4 width of cloth striped difference figure, figure carries out Threshold Segmentation, filtering to the striped difference, and utilizes the boundary information among the wrapped phase figure that the border of each cycle striped is positioned;
    Step 4.1.1: adopt less threshold value that every width of cloth striped difference figure is carried out Threshold Segmentation, gray-scale value belongs to greater than the point of this threshold value and is non-0 value striped, and it is 1 that gray-scale value is composed, otherwise to compose be 0 to gray-scale value;
    Gray-scale value is 0 point among the step 4.1.2:4 width of cloth striped difference figure, is defined as dash area, and this part does not participate in following any calculating;
    Step 4.1.3: adopt the contrast filtering algorithm to eliminate noise to the striped difference figure after the Threshold Segmentation; Under same coordinate, the position zero lap of all the 0 value stripeds among 4 width of cloth striped difference figure and be covered with non-shaded portion, therefore concerning 4 width of cloth striped difference figure, noise among a certain width of cloth striped difference figure inevitable with other figure in the coordinate of 0 value striped overlapping, because the width of 0 discrete value striped and width and the scope that scope is far longer than noise, so but by the contrast filtering noise to scope;
    Step 4.1.4: determine each striped border: every some phase place in the wrapped phase is asked for phase gradient according to wrapped phase
    Figure FSB00000315993300031
    Wherein, (x y) is the coordinate of wrapped phase figure mid point, grad (x, y) be (x, phase gradient y),
    Figure FSB00000315993300032
    Figure FSB00000315993300033
    Be wrapped phase, phase gradient is the striped frontier point greater than the point of gradient mean value;
    Step 4.1.5: to the gray-scale value among the filtered poor figure is 0 striped, if its most zones are positioned at certain two border, then with the boundary line of these two borders as 0 value striped, thereby accurately locatees each 0 value striped;
    Step 4.2: determine malposition fringes raster pattern I ' oComposition sequence, malposition fringes I ' oIn, be that 0 phase-shifted grating and malposition fringes grating subtract each other the identical position of 0 value striped among the poor figure that obtains with initial phase, corresponding striped is a ', the striped that a ' obtains for a distortion; Be that the phase-shifted grating of 0.5 π and malposition fringes grating subtract each other the identical position of 0 value striped among the poor figure that obtains with initial phase, corresponding striped is b ', the striped that b ' obtains for the b distortion; Be that the phase-shifted grating of π and malposition fringes grating subtract each other the identical position of 0 value striped among the poor figure that obtains with initial phase, corresponding striped is c ', the striped that c ' obtains for the c distortion; Be that the phase-shifted grating of 1.5 π and malposition fringes grating subtract each other the identical position of 0 value striped among the poor figure that obtains with initial phase, corresponding striped is d ', the striped that d ' obtains for the d distortion;
    Step 4.3: determine the accurate order of each monocycle striped in the malposition fringes grating, to I ' oIn each monocycle striped, two monocycle stripeds that are adjacent are formed one 3 cycle striped sequence, at I oThe unique sequence corresponding with it of middle searching, corresponding fringe order is inferior identical in two sequences, promptly draws the accurate order of each monocycle striped in the malposition fringes grating thus.
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